sslv3 alert illegal parameter

I'm having trouble connecting to my stunnel server. Both the client
and server are running Ubuntu stunnel4. The connection log (from the
server) is as follows:

sshd accepted FD=8 from [censored]:35982
sshd started
FD 8 in non-blocking mode
TCP_NODELAY option set on local socket
FD 9 in non-blocking mode
FD 10 in non-blocking mode
Cleaning up the signal pipe
Connection from [censored]:35982 permitted by libwrap
sshd accepted connection from [censored]:35982
Child process 10251 finished with code 0
SSL state (accept): before/accept initialization
SSL state (accept): SSLv3 read client hello A
SSL state (accept): SSLv3 write server hello A
SSL state (accept): SSLv3 write certificate A
SSL state (accept): SSLv3 write certificate request A
SSL state (accept): SSLv3 flush data
SSL alert (read): fatal: illegal parameter
SSL_accept: 14094417: error:14094417:SSL
routines:SSL3_READ_BYTES:sslv3 alert illegal parameter
Connection reset: 0 bytes sent to SSL, 0 bytes sent to socket
sshd finished (0 left)

The client reports the following:

Snagged 64 random bytes from /path/to/.rnd
Wrote 1024 new random bytes to /path/to/.rnd
RAND_status claims sufficient
entropy for the PRNG
PRNG seeded successfully
Certificate: /path/to/.stunnel/certificates/host.crt
Certificate loaded
Key file: /path/to/.stunnel/keys/host.key
Private key loaded
Loaded verify certificates from /path/to/.stunnel/certificates/
cert.crt
Loaded /path/to/.stunnel/certificates/cert.crt revocation lookup
file
SSL context initialized for service stunnel
ssh_exchange_identification: Connection closed by remote host

Is this a handshake problem? (But I'm using the same stunnel on both
sides!?!?). I don't think my server configuration is at fault, as I've
been able to connect to it using other stunnel clients. I have the
feeling this has something to do with my version of OpenSSL - can
someone confirm? My stunnel/ssl info is as follows:

>$ /usr/sbin/stunnel -version
stunnel 4.20 on i486-pc-linux-gnu with OpenSSL 0.9.8e 23 Feb 2007
Threading:PTHREAD SSL:ENGINE Sockets:POLL,IPv6 Auth:LIBWRAP

Global options
debug = 5
pid = /var/run/stunnel4.pid
RNDbytes = 64
RNDfile = /dev/urandom
RNDoverwrite = yes

Service-level options
cert = /etc/stunnel/stunnel.pem
ciphers = ALL:!ADH:+RC4:@STRENGTH
key = /etc/stunnel/stunnel.pem
session = 300 seconds
sslVersion = SSLv3 for client, all for server
TIMEOUTbusy = 300 seconds
TIMEOUTclose = 60 seconds
TIMEOUTconnect = 10 seconds
TIMEOUTidle = 43200 seconds
verify = none

Thanks!